U.S. Pat. No. 3,721,355 of Mar. 20, 1973 for "Vehicle Mounted Loader and Unloader" by Joseph F. Irving discloses a mechanism of the type of this invention wherein a base structure is mounted on the side of a vehicle bed so that it can be moved along the length of the bed to align it with loads to be transferred between the bed and an area beside the vehicle. An inner boom is shown mounted on the base for pivotal motion around a coupling having an axis parallel to the vehicle side. This coupling is mounted within the width limit of the vehicle and therefore imposes restrictions on the arc of motion of the inner boom in the region above the level of the vehicle bed thereby limiting the range of motion of the load transfer mechanism supported on an outer boom pivotally coupled to the inner boom.
It has been found that the load transfer mechanism of U.S. Pat. No. 3,721,355 is often positioned along the vehicle side in a less than optimum position for picking up or depositing the load as where the vehicle is not positioned with its desired load carrying area in precise transverse alignment with the area adjacent the vehicle in which the load is to be picked up or deposited. Both the transverse range and longitudinal range of load manipulation have been limited such that even a skilled vehicle driven and unloader operator have been required to make extra adjustments of the vehicle and unloader in order to complete a load transfer.
The mechanism of U.S. Pat. No. 3,721,355 is ordinarily installed on a completed truck. Installation has involved substantial time and effort where the load transfer unit is installed separately from the power unit supplying the power to operate the load transfer unit. Where a unitary assembly of a load transfer mechanism and a power unit was provided to enable installation of a single unit and to avoid the need for installing connections between the units, the fixed mounting of the power unit limited the range of motion of the assembly along the side of the vehicle. The power unit mounted within the vehicle width limits could not clear the vehicle wheels or any other elements depending from the bed along its margin.
In accordance with the above an object of the present invention is to improve a vehicle mounted loader and unloader.
Another object is to increase to versatility of a vehicle mounted loader and unloader by increasing the load capacity of the mechanism and increasing its range of motion.
A further object is to enable a vehicle mounted loader and unloader adapted for motion along the side of the vehicle to be moved along the side while under load.
A fourth object is to drive a vehicle mounted loader and unloader along the side of the vehicle and to drive the extension and retraction of the load manipulating means transverse of the vehicle even when carrying a load.
A fifth object is to stabilize a vehicle mounted loader and unloader assembly against unbalanced loading over the entire range of travel of the assembly along the side of a vehicle.